Refractory support device and associated method

ABSTRACT

A refractory anchoring system that mitigates the effects of the thermo-mechanical stresses that arise from the furnace temperature gradient and varying thermal expansions of the refractory and casing. This anchoring system provides independent movement which may be important for maintaining the refractory lining stability and its ability to contain the furnace processes. The invention relates more specifically to the metallic member that is configured in a specific spring-like manner. This invention also relates to the specific design of the non-metallic member (refractory anchor) to work in conjunction with the metallic member.

FIELD OF INVENTION

The present invention relates generally to the refractory arts, moreparticularly to a support system that attaches the refractory to afurnace casing so that each can move independently of each other withthe thermal expansion of the refractory in a furnace environment. Thisindependent movement may be important for maintaining the refractorylining stability and its ability to contain the furnace processes. Thisinvention maybe found applicable to other structures in which theadvantages hereinafter pointed out would be useful.

BACKGROUND OF INVENTION

Refractories are heat resistant materials that are used as a means tocontain a process and/or used as insulation to reduce heat loss(increase efficiency) in industrial applications requiring hightemperatures such as metallurgical processing, incineration, refining,cement manufacturing, power generation, glass manufacturing,ceramic/brick manufacturing, etc. The refractory generally lines theinterior of a metal casing which provides support for the process andrefractory. The refractory is secured to the casing utilizing the casinggeometry (arch type construction) or with various types of supportdevices (anchors). The anchors consist of a metallic alloy assemblysecured to the shell by means of welding, bolting, clipping, etc. andcan be used independently or in conjunction with a refractory (ceramic)anchor.

Ceramic anchors are generally required for most applications when, thetemperature exceed the limitations of alloy anchors, corrosiveatmospheres limit alloy anchors, supplemental anchor holding power isrequired, multiple component linings or support surface area is neededto hold the refractory during installation. Anchors made like a pre-castcastable shape are also considered as ceramic anchor even though they donot have ceramic bonding. Ceramic anchors are often viewed as a“necessary evil”. This is due to the multitude of refractory liningfailures that have been blamed on the anchor and/or its orientation. Thethermal conditions within a furnace environment impart stresses into therefractory and the refractory support system which ultimately leads torefractory failures. This application provides a utilitarian design ofan anchoring system that mitigates the effects of the thermo-mechanicalstresses that arise from the furnace temperature gradient and varyingthermal expansions of the refractory and casing.

SUMMARY OF THE INVENTION

This application discloses a furnace wall assembly comprising: anexterior wall having an inner face; an interior refractory wallcomprising: an insulating layer adjacent to the exterior wall innerface; and a hotface layer adjacent to the insulating layer such that theinsulating layer is disposed between the exterior wall inner face andthe hotface layer, the hotface layer movable from a first position to asecond position when subjected to thermal energy; an anchor having afirst end and a second end, the anchor first end adjacent to theexterior wall inner face and the anchor second end extending into thehotface layer of the interior refractory wall, wherein the anchor ismovable from a first lateral position to a second lateral position whenthe hotface layer moves from the hotface layer first position to thehotface layer second position; and a support having a first end rigidlycoupled to the exterior wall inner face and slidingly engaging theanchor in the anchor first lateral position, and wherein the supportfurther engages the anchor when the anchor is moved to the second anchorposition.

This application also discloses a furnace wall assembly comprising: anexterior wall having an inner face; an interior refractory wall adjacentto the exterior wall inner face, the interior refractory wall movablefrom a first position to a second position when subjected to thermalenergy; an anchor having a first end and a second end, the anchor firstend adjacent to the exterior wall inner face and the anchor second endextending into the interior refractory wall, wherein the anchor ismovable from a first lateral position to a second lateral position whenthe interior refractory wall moves from the interior refractory wallfirst position to the interior refractory wall second position; and asupport having a first end rigidly coupled to the exterior wall innerface and slidingly engaging the anchor in the anchor first lateralposition, and wherein the support further engages the anchor when theanchor is moved to the second anchor position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangementsof parts, an illustrative embodiment of which will be described indetail in the specification and illustrated in the accompanying drawingswith form a part hereof, and wherein:

FIG. 1 is perspective view of partial refractory line wall structureillustrating an embodiment of the present invention.

FIG. 2 is perspective view of the metallic and ceramic anchor systemmounted on a furnace sidewall. The refractory lining is not shown forclarification.

FIG. 3 is a sectional view of the metallic anchor and ceramic anchorconfiguration before and after attachment.

FIG. 4 is a perspective view of a representation of the prior art.

FIG. 5 is a sectional view of the prior art shown in FIG. 4.

FIG. 6 is a sectional view of the prior art and illustrates movement dueto thermal strain.

FIG. 7 is a sectional view of an embodiment and illustrates movement dueto thermal strain.

FIG. 8 shows examples of how a spring-like assembly claimed in thisinvention can be used in conjunction with prior art and otherconfigurations

DETAILED DESCRIPTION

Referring now to the drawings wherein the drawings are for the purposeof illustrating an embodiment of the invention only, and not for thepurpose of limiting the same.

FIG. 1 is a perspective view of a partially assembled furnace wallstructure 10, illustrating an embodiment of the present invention.Furnace wall structure 10 depicted in the drawing shows a refractorywall structure that could represent the interior of any industrialfurnace application. The furnace wall structure 10 is comprised of ametallic panel 100 that form the outer casing of the structure and atwo-component refractory wall 20 that is formed by an insulating layerof refractory 30 and a hotface layer of refractory 40. The refractory isattached to the furnace wall with a metallic spring support 50 and aceramic anchor 60. FIG. 1 also shows a layer of compressible material 70wrapped around the spring support to provide an area within therefractory for movement to occur.

FIG. 2 is an isolated, perspective view of the embodiment consisting ofa metallic spring support 50 and ceramic anchor 60 system mounted on afurnace casing 100. The refractory lining is not shown for clarity.

FIG. 3 is a sectional view of the metallic spring support 50 and ceramicanchor 60 configuration before and after the ceramic anchor 60 ismounted into the support. FIG. 3 illustrates the mating of a corrugatedspiral 110 formed in the configuration of a ceramic anchor 60 with ametallic spring support 50. The base of the metallic spring support isshown so that the attachment point (weld) 115 is located on either theouter diameter of the spring 120 and on the inner diameter of the spring125.

FIG. 4 is a perspective view of a representation of the prior artconsisting of a metallic furnace wall panel 100 with a C-shaped memberalloy support “C-clip” 300 that contains a standardized shape ceramicanchor 310.

FIG. 5 is a sectional view of the prior art shown in FIG. 4. This viewshows the gap 240 between the ceramic anchor 310 and the C-clip 300. Awedge 245 must be installed in the gap 240 to support the ceramic anchor310 in the proper position prior to the refractory installation.

The present invention thus provides a unique apparatus for supportingthe refractory lining to the interior of a furnace and allows therefractory to move independently from the furnace casing. The inventionallows for any and all movement in any direction parallel to the furnacecasing and also movement away from the casing (toward the furnaceinterior). The amount of movement allowed may be limited by thecharacteristics of the spring support system.

FIG. 6 represents a is a sectional view of the furnace wall structure 10that is comprised of a metallic panel 100 that form the outer casing ofthe structure and a two-component refractory wall 20 that is formed byan insulating layer of refractory 30 and a hotface layer of refractory40. The refractory is attached to the furnace wall with the prior artconsisting of a C-clip 300 and a standardized ceramic anchor 310. Athermal strain 200 resulting from the furnace environment (shown asarrows) causes a deflection 205 in the refractory lining. The deflection205 can cause a unidirectional, bi-directional or shear load on theceramic anchor 310. In this prior art, this stress is transferred to the“ears” 285 of the ceramic anchor 310 creating a bending moment (tension)and ultimate failure 272 as ceramics are extremely brittle and havelittle tensile strength. The amount of stress in the ceramic anchor ear285 is related to the total amount of deflection 205 beyond thedeflection 208 that is allowed for in the C-clip. This type of failureis very common in many refractory installations.

FIG. 7 is a sectional view of the embodiment showing a furnace wallstructure 10 that is comprised of a metallic panel 100 that form theouter casing of the structure and a two-component refractory wall 20that is formed by an insulating layer of refractory 30 and a hotfacelayer of refractory 40. The refractory is attached to the furnace wallwith a metallic spring support 50 and a ceramic anchor 60. A layer ofcompressible material 70 wrapped around the spring support to provide anarea of growth. FIG. 7 illustrates that the as the hotface refractorylayer 40 is subjected to thermal strain 200 and movement as representedas arrows, the invention allows for movement of the metallic spring 50and ceramic anchor 60 in the direction of the force. The shadow drawing215 represents the original position of the anchor system. Thecompressible material 70 is compressed 72 in the direction of therefractory movement.

In addition to allowing the movement of the refractory lining, anadvantage of the present invention is that the spring supports willdistributes stresses developed from the thermal expansion of the liningthroughout the entire length of the spring support and across manycorrugations of the ceramic anchor rather than create a bending momentat one ear as does the prior art allows. Another advantage is that thespring support is active in holding the ceramic anchor along the entirelength of the spring. This results in a larger surface area where theanchor meets the spring support which reduces the amount of localizedstress between the anchor and the support.

The closer the anchor retention point is to the working environment ofthe furnace the hotter the anchor becomes. As the metallic anchorbecomes hotter the strength properties of the metal substantiallydecrease thus creating a weaker support. In the prior art, the anchorretention area is fixed at about 3″ away from the furnace casingcompared the present invention where the anchor retention extends from3″ away from the casing to the casing proper. This provides a largersection of the metallic anchor in contact with the ceramic anchor thatis at a substantially cooler and stronger condition.

The illustrative ceramic anchor is this invention has a roundedcross-section. The round shape will induce less stress and resultingcracking of the refractory than the prior art of square cross-sectionalceramic anchors which tend to induce stress riser in the cornersespecially on the furnace interior. The rounded cross-section of theceramic anchor in the illustrative embodiment can help eliminate voidsand shadows when installing the refractory as compared to the squareconfiguration of the prior art.

In this embodiment, the overall apparent length of the anchor (and thusthe thickness of the refractory lining) is adjustable as the ceramicanchor does not have to be tightened all the way to the furnace casing.In this embodiment, the metallic anchor support and ceramic anchor areadditive and can be joined in multiple sections to achieve variouslining thicknesses.

Because of the C-clip gap in the prior art, the ceramic anchor has to bewedged into place to hold it securely during the refractoryinstallation. Typically two small wooden wedges are used. Manyapplications the wooden wedge does not get hot enough to burn andcontinues to hold the brick tightly against the ears of the C-clip thusgiving rise to additional stress in the prior art. No wedges arenecessary with the illustrative embodiment which eliminates this sourceof stress and facilitates the installation.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed. For example, as illustrated in FIG. 8 shows examples of how aspring-like assembly claimed in this invention can be used inconjunction with prior art, namely standardized ceramic anchors and thesupport clips to increase the utility of the prior system. Spring designmodifications may include changes to the number of coils, curvatures,flat springs, dimensional springs, orientation, Hooke's law constants,alloys, diameters, and attachment methods. Ceramic anchor modificationsmay include changes to the anchor dimensions, corrugations dimensions,spiral dimensions, methods to attach to the spring clip, internal (male)springs, external (female) springs, anchor material composition, anchorfabrication method, metallic anchors, pre-cast blocks, brick anchors orinterlocking tiles. Installation practices may be modified to includechanges to the application of the compressible material, composition ofthe compressible material, anchor spacings, use of multiple anchors typein conjunction with the invention, various applications, various furnaceconfigurations or non-refractory applications.

1. A furnace wall assembly comprising: an exterior wall having an innerface; an interior refractory wall comprising: an insulating layeradjacent to the exterior wall inner face; and a hotface layer adjacentto the insulating layer such that the insulating layer is disposedbetween the exterior wall inner face and the hotface layer, the hotfacelayer movable from a first position to a second position when subjectedto thermal energy; an anchor having a first end and a second end, theanchor first end adjacent to the exterior wall inner face and the anchorsecond end extending into the hotface layer of the interior refractorywall, wherein the anchor is movable from a first lateral position to asecond lateral position when the hotface layer moves from the hotfacelayer first position to the hotface layer second position; and a supporthaving a first end rigidly coupled to the exterior wall inner face andslidingly engaging the anchor in the anchor first lateral position, andwherein the support further engages the anchor when the anchor is movedto the second anchor position.
 2. The furnace wall assembly of claim 1wherein the exterior wall is formed from a metal.
 3. The furnace wallassembly of claim 1 wherein at least one of the insulating layer andhotface layer is formed from a ceramic.
 4. The furnace wall assembly ofclaim 1 wherein the anchor includes a helical thread.
 5. The furnacewall assembly of claim 1 wherein the support is a compression spring. 6.The furnace wall assembly of claim 1 wherein the exterior wall is formedfrom concrete.
 7. The furnace wall assembly of claim 1 wherein theexterior wall is formed from a composite material.
 8. The furnace wallassembly of claim 1 further comprising a compressible member disposedabout the support near the support first end.
 9. A furnace wall assemblycomprising: an exterior wall having an inner face; an interiorrefractory wall adjacent to the exterior wall inner face, the interiorrefractory wall movable from a first position to a second position whensubjected to thermal energy; an anchor having a first end and a secondend, the anchor first end adjacent to the exterior wall inner face andthe anchor second end extending into the interior refractory wall,wherein the anchor is movable from a first lateral position to a secondlateral position when the interior refractory wall moves from theinterior refractory wall first position to the interior refractory wallsecond position; and a support having a first end rigidly coupled to theexterior wall inner face and slidingly engaging the anchor in the anchorfirst lateral position, and wherein the support further engages theanchor when the anchor is moved to the second anchor position.
 10. Thefurnace wall assembly of claim 9 wherein the exterior wall is formedfrom a metal.
 11. The furnace wall assembly of claim 9 wherein interiorrefractory wall is formed from a ceramic.
 12. The furnace wall assemblyof claim 9 wherein the anchor includes a helical thread.
 13. The furnacewall assembly of claim 9 wherein the support is a compression spring.14. The furnace wall assembly of claim 9 wherein the exterior wall isformed from concrete.
 15. The furnace wall assembly of claim 9 whereinthe exterior wall is formed from a composite material.
 16. The furnacewall assembly of claim 9 further comprising a compressible memberdisposed about the support near the support first end.